Gazelle–livestock interactions and impact of water resource development in the Ouadi Rimé– Ouadi AchimReserve, Chad TIM WAC H E R,RAJAN AMIN ,JOHN NEWBY


MAHAMAT HASSAN HAT C H A,KRAZ I DI ABEY E,HAB IB ALI SADOCK ZEUBO BE BOURTCHI A K B É and F ELIX NDOASSAL B ANLONGAR


Abstract The Ouadi Rimé–Ouadi Achim Reserve (Réserve de l’Ouadi Rimé–Ouadi Achim) in central Chad supports large numbers of livestock and rare antelopes, and is the site of ongoing reintroductions of the scimitar-horned oryx Oryx dammah and addax Addax nasomaculatus.We present results of surveys conducted during 2011–2019 to examine patterns of relative abundance and distribution of dorcas gazelles Gazella dorcas, dama gazelles Nanger dama and livestock in relation to each other and to water sources in a 3,500 km2 area in the centre of the Reserve. Dorcas ga- zelles numbered 7,700–18,000, moving extensively across the area. Livestock varied between c. 2,000 and 68,000 trop- ical livestock units across surveys, with density doubling in the wet season. Dorcas gazelle distribution was negatively associated with livestock, and livestock density was positively associated with artificial water sources. Dorcas gazelle dens- ities were positively associated with locations where there had been wild fires in the 6 months prior to a survey. Dama gazelles were encountered only 13 times, insufficient to esti- mate theirpopulation size reliably. Opportunistic observations suggest dama gazelles avoid livestock and burnt ground. Our findings highlight the importance of the Reserve.We recom- mend the designation of a large, well-managed conservation priority zone in the Reserve’s core area in which no further development of water resources is permitted. Management of livestock numbers within this zone at or below current levels is essential to integrate national goals for both biodiversity conservation and pastoralism development.


Keywords Chad, dama gazelle, dorcas gazelle, livestock, Ouadi Rimé–Ouadi Achim Reserve, pastoralism, Sahel, sustainable development


Introduction


Chad is one of only a few protected areas, and by far the largest, representing Africa’s vast Sahelian grassland biome (Brugiere & Scholte, 2013; Protected Planet, 2020).When le- gally established as an IUCN category IV reserve in 1969, the objective was to protect significant populations of threat- ened Sahelo–Saharan endemic species (Newby, 1978) such as the scimitar-horned oryx Oryx dammah (categorized on the IUCN Red List as Extinct in the Wild; IUCN/SSC Antelope Specialist Group, 2016c), dorcas gazelle Gazella dorcas (Vulnerable; IUCN/SSC Antelope Specialist Group, 2017), dama gazelle Nanger dama (Critically Endangered; IUCN/SSC Antelope Specialist Group, 2016b) and addax Addax nasomaculatus (Critically Endangered; IUCN/SSC Antelope Specialist Group, 2016a). The Reserve also sup- ported the North African ostrich Struthio camelus,Arabian Ardeotis arabs, Nubian Ardeotis nuba and Denham’s Neotis denhami bustards, and small populations of theWestAfrican cheetah Acinonyx jubatus and African wild dog Lycaon pictus. Traditional transhumant livestock management, originally low impact and highly seasonal, has always been permitted in the Reserve, but hunting and tree cutting are banned. The populations of oryx, addax and ostrich were extirpated during a period of civil unrest in the late 1970s and early 1980s (Newby, 1978, 1980, 1988). The scimitar- horned oryx was first categorized as Extinct in the Wild on the IUCN Red List in 2000. Since the 1970s, as elsewhere (De Leeuw&Tothill, 1990), development and anthropogen- ic pressures such as density of people and livestock, water use, grazing pressure, disturbance, vehicle traffic and grass fires have increased in the Reserve. Following the decision of the Government of Chad to


T TIM WACHER (Corresponding author, orcid.org/0000-0002-5552-7577,


tim.wacher@zsl.org) and RAJAN AMIN Conservation & Policy, Zoological Society of London, London, NW1 4RY, UK


JOHN NEWBY Sahara Conservation Fund, Saint Maur des Fossés, France KRAZIDI ABEYE and HABIB ALI Sahara Conservation Fund, N’Djamena, Chad


MAHAMAT HASSAN HATCHA,SADOCK ZEUBOBE BOURTCHIAKBÉ and FELIX NDOASSAL BANLONGAR Direction de la Faune et des Aires Protégées, N’Djamena, Chad


Received 27 April 2021. Revision requested 29 July 2021. Accepted 27 October 2021. First published online 25 May 2022.


support the restoration of the scimitar-horned oryx and other wildlife populations (Bemadjin et al., 2012), we as- sessed numbers and spatial interactions between dorcas and dama gazelles and livestock in the Reserve. This study is based on transect surveys conducted to assess the feasibil- ity of reintroducing the oryx to the area, and continued dur- ing the initial stages of this reintroduction. We report on trends in densities and distribution of the gazelles and live- stock, based on data from eight large-scale, vehicle-based


This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Oryx, 2023, 57(2), 205–215 © The Author(s), 2022. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605321001629


he 77,950 km2 Ouadi Rimé–Ouadi Achim Reserve (Réserve de l’Ouadi Rimé–Ouadi Achim) in central


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